LuaJava_07 - can Java detect the original type of Lua values?

When LuaJava is used to invoke Java methods, some of the given (Lua) arguments will be converted, others will not. Is it possible to detect the original type of an (unconverted) Lua argument? LuaJava_07 goes further into this question.

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LuaJava_07

The script itself is extremely simple and should not require any further explanation. The accompanying Java source may be compiled using
 

  javac LuaJava_07.java

and will (again) need the luajava package. The resulting class file should be copied to a place where it can be found by the Java class loader (e.g., into a directory which is automatically scanned by the Java extension mechanism).

After an invocation of the form
 

  java luna.LuaJava LuaJava_07.lua

the script produces the following output

LuaJava_07 - can Java detect the original Lua type?

  Lua2Java(nil)            -> null (null)
  Lua2Java(true)           -> java.lang.Boolean(true)
  Lua2Java(123.456)        -> java.lang.Integer(123)
  Lua2Java('Test')         -> java.lang.String(Test)
  Lua2Java({})             -> Lua Table (Lua Table)
  Lua2Java(function() end) -> Lua Function (Lua Function)

Some details are worth mentioning:

• Lua numbers seem to be converted to Java Integer objects - this should be the reason why numbers get truncated when passed from Lua to Java;
• Lua values which cannot be (easily) converted to a Java type will be passed as a LuaObject - Java then has the chance to determine the original type of the Lua value;

Source Code

The source code of this script and its accompanying Java class is publically available:

• LuaJava_07.lua
• LuaJava_07.java

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